Generally, you are writing a persuasive essay, yes. You should always acknowledge the other side - the topics they give us are ones on which reasonable people can disagree.
Your general attitude is, well, yes, some people will think ABC and that's sometimes the case, but most of the time, it's really XYZ, and here's why.
Don't spend too much time discussing the other side, though - that's a much harder essay to write, and you only have 30 minutes start to finish. Your primary goal is to write a good-enough essay that doesn't tire you out before the multiple choice. I generally only "acknowledge the other side" in the intro and conclusion.
This article may be of interest to you:
http://www.beatthegmat.com/mba/2009/12/ ... -no-thanks